Actual source code: sfwindow.c

petsc-3.9.2 2018-05-20
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  1:  #include <petsc/private/sfimpl.h>

  3: typedef struct _n_PetscSFDataLink *PetscSFDataLink;
  4: typedef struct _n_PetscSFWinLink  *PetscSFWinLink;

  6: typedef struct {
  7:   PetscSFWindowSyncType sync; /* FENCE, LOCK, or ACTIVE synchronization */
  8:   PetscSFDataLink       link;   /* List of MPI data types and windows, lazily constructed for each data type */
  9:   PetscSFWinLink        wins;   /* List of active windows */
 10: } PetscSF_Window;

 12: struct _n_PetscSFDataLink {
 13:   MPI_Datatype    unit;
 14:   MPI_Datatype    *mine;
 15:   MPI_Datatype    *remote;
 16:   PetscSFDataLink next;
 17: };

 19: struct _n_PetscSFWinLink {
 20:   PetscBool      inuse;
 21:   size_t         bytes;
 22:   void           *addr;
 23:   MPI_Win        win;
 24:   PetscBool      epoch;
 25:   PetscSFWinLink next;
 26: };

 28: const char *const PetscSFWindowSyncTypes[] = {"FENCE","LOCK","ACTIVE","PetscSFWindowSyncType","PETSCSF_WINDOW_SYNC_",0};

 30: /* Built-in MPI_Ops act elementwise inside MPI_Accumulate, but cannot be used with composite types inside collectives (MPIU_Allreduce) */
 31: static PetscErrorCode PetscSFWindowOpTranslate(MPI_Op *op)
 32: {

 35:   if (*op == MPIU_SUM) *op = MPI_SUM;
 36:   else if (*op == MPIU_MAX) *op = MPI_MAX;
 37:   else if (*op == MPIU_MIN) *op = MPI_MIN;
 38:   return(0);
 39: }

 41: /*@C
 42:    PetscSFWindowGetDataTypes - gets composite local and remote data types for each rank

 44:    Not Collective

 46:    Input Arguments:
 47: +  sf - star forest
 48: -  unit - data type for each node

 50:    Output Arguments:
 51: +  localtypes - types describing part of local leaf buffer referencing each remote rank
 52: -  remotetypes - types describing part of remote root buffer referenced for each remote rank

 54:    Level: developer

 56: .seealso: PetscSFSetGraph(), PetscSFView()
 57: @*/
 58: static PetscErrorCode PetscSFWindowGetDataTypes(PetscSF sf,MPI_Datatype unit,const MPI_Datatype **localtypes,const MPI_Datatype **remotetypes)
 59: {
 60:   PetscSF_Window    *w = (PetscSF_Window*)sf->data;
 61:   PetscErrorCode    ierr;
 62:   PetscSFDataLink   link;
 63:   PetscInt          i,nranks;
 64:   const PetscInt    *roffset,*rmine,*rremote;
 65:   const PetscMPIInt *ranks;

 68:   /* Look for types in cache */
 69:   for (link=w->link; link; link=link->next) {
 70:     PetscBool match;
 71:     MPIPetsc_Type_compare(unit,link->unit,&match);
 72:     if (match) {
 73:       *localtypes  = link->mine;
 74:       *remotetypes = link->remote;
 75:       return(0);
 76:     }
 77:   }

 79:   /* Create new composite types for each send rank */
 80:   PetscSFGetRanks(sf,&nranks,&ranks,&roffset,&rmine,&rremote);
 81:   PetscNew(&link);
 82:   MPI_Type_dup(unit,&link->unit);
 83:   PetscMalloc2(nranks,&link->mine,nranks,&link->remote);
 84:   for (i=0; i<nranks; i++) {
 85:     PETSC_UNUSED PetscInt rcount = roffset[i+1] - roffset[i];
 86:     PetscMPIInt           *rmine,*rremote;
 87: #if !defined(PETSC_USE_64BIT_INDICES)
 88:     rmine   = sf->rmine + sf->roffset[i];
 89:     rremote = sf->rremote + sf->roffset[i];
 90: #else
 91:     PetscInt j;
 92:     PetscMalloc2(rcount,&rmine,rcount,&rremote);
 93:     for (j=0; j<rcount; j++) {
 94:       PetscMPIIntCast(sf->rmine[sf->roffset[i]+j],rmine+j);
 95:       PetscMPIIntCast(sf->rremote[sf->roffset[i]+j],rremote+j);
 96:     }
 97: #endif
 98:     MPI_Type_create_indexed_block(rcount,1,rmine,link->unit,&link->mine[i]);
 99:     MPI_Type_create_indexed_block(rcount,1,rremote,link->unit,&link->remote[i]);
100: #if defined(PETSC_USE_64BIT_INDICES)
101:     PetscFree2(rmine,rremote);
102: #endif
103:     MPI_Type_commit(&link->mine[i]);
104:     MPI_Type_commit(&link->remote[i]);
105:   }
106:   link->next = w->link;
107:   w->link    = link;

109:   *localtypes  = link->mine;
110:   *remotetypes = link->remote;
111:   return(0);
112: }

114: /*@C
115:    PetscSFWindowSetSyncType - set synchrozitaion type for PetscSF communication

117:    Logically Collective

119:    Input Arguments:
120: +  sf - star forest for communication
121: -  sync - synchronization type

123:    Options Database Key:
124: .  -sf_window_sync <sync> - sets the synchronization type FENCE, LOCK, or ACTIVE (see PetscSFWindowSyncType)

126:    Level: advanced

128: .seealso: PetscSFSetFromOptions(), PetscSFWindowGetSyncType()
129: @*/
130: PetscErrorCode PetscSFWindowSetSyncType(PetscSF sf,PetscSFWindowSyncType sync)
131: {

137:   PetscUseMethod(sf,"PetscSFWindowSetSyncType_C",(PetscSF,PetscSFWindowSyncType),(sf,sync));
138:   return(0);
139: }

141: static PetscErrorCode PetscSFWindowSetSyncType_Window(PetscSF sf,PetscSFWindowSyncType sync)
142: {
143:   PetscSF_Window *w = (PetscSF_Window*)sf->data;

146:   w->sync = sync;
147:   return(0);
148: }

150: /*@C
151:    PetscSFWindowGetSyncType - get synchrozitaion type for PetscSF communication

153:    Logically Collective

155:    Input Argument:
156: .  sf - star forest for communication

158:    Output Argument:
159: .  sync - synchronization type

161:    Level: advanced

163: .seealso: PetscSFGetFromOptions(), PetscSFWindowSetSyncType()
164: @*/
165: PetscErrorCode PetscSFWindowGetSyncType(PetscSF sf,PetscSFWindowSyncType *sync)
166: {

172:   PetscUseMethod(sf,"PetscSFWindowGetSyncType_C",(PetscSF,PetscSFWindowSyncType*),(sf,sync));
173:   return(0);
174: }

176: static PetscErrorCode PetscSFWindowGetSyncType_Window(PetscSF sf,PetscSFWindowSyncType *sync)
177: {
178:   PetscSF_Window *w = (PetscSF_Window*)sf->data;

181:   *sync = w->sync;
182:   return(0);
183: }

185: /*@C
186:    PetscSFGetWindow - Get a window for use with a given data type

188:    Collective on PetscSF

190:    Input Arguments:
191: +  sf - star forest
192: .  unit - data type
193: .  array - array to be sent
194: .  epoch - PETSC_TRUE to acquire the window and start an epoch, PETSC_FALSE to just acquire the window
195: .  fenceassert - assert parameter for call to MPI_Win_fence(), if PETSCSF_WINDOW_SYNC_FENCE
196: .  postassert - assert parameter for call to MPI_Win_post(), if PETSCSF_WINDOW_SYNC_ACTIVE
197: -  startassert - assert parameter for call to MPI_Win_start(), if PETSCSF_WINDOW_SYNC_ACTIVE

199:    Output Arguments:
200: .  win - window

202:    Level: developer

204:    Developer Notes:
205:    This currently always creates a new window. This is more synchronous than necessary. An alternative is to try to
206:    reuse an existing window created with the same array. Another alternative is to maintain a cache of windows and reuse
207:    whichever one is available, by copying the array into it if necessary.

209: .seealso: PetscSFGetRanks(), PetscSFWindowGetDataTypes()
210: @*/
211: static PetscErrorCode PetscSFGetWindow(PetscSF sf,MPI_Datatype unit,void *array,PetscBool epoch,PetscMPIInt fenceassert,PetscMPIInt postassert,PetscMPIInt startassert,MPI_Win *win)
212: {
213:   PetscSF_Window *w = (PetscSF_Window*)sf->data;
215:   MPI_Aint       lb,lb_true,bytes,bytes_true;
216:   PetscSFWinLink link;

219:   MPI_Type_get_extent(unit,&lb,&bytes);
220:   MPI_Type_get_true_extent(unit,&lb_true,&bytes_true);
221:   if (lb != 0 || lb_true != 0) SETERRQ(PetscObjectComm((PetscObject)sf),PETSC_ERR_SUP,"No support for unit type with nonzero lower bound, write petsc-maint@mcs.anl.gov if you want this feature");
222:   if (bytes != bytes_true) SETERRQ(PetscObjectComm((PetscObject)sf),PETSC_ERR_SUP,"No support for unit type with modified extent, write petsc-maint@mcs.anl.gov if you want this feature");
223:   PetscNew(&link);

225:   link->bytes = bytes;
226:   link->addr  = array;

228:   MPI_Win_create(array,(MPI_Aint)bytes*sf->nroots,(PetscMPIInt)bytes,MPI_INFO_NULL,PetscObjectComm((PetscObject)sf),&link->win);

230:   link->epoch = epoch;
231:   link->next  = w->wins;
232:   link->inuse = PETSC_TRUE;
233:   w->wins     = link;
234:   *win        = link->win;

236:   if (epoch) {
237:     switch (w->sync) {
238:     case PETSCSF_WINDOW_SYNC_FENCE:
239:       MPI_Win_fence(fenceassert,*win);
240:       break;
241:     case PETSCSF_WINDOW_SYNC_LOCK: /* Handled outside */
242:       break;
243:     case PETSCSF_WINDOW_SYNC_ACTIVE: {
244:       MPI_Group ingroup,outgroup;
245:       PetscSFGetGroups(sf,&ingroup,&outgroup);
246:       MPI_Win_post(ingroup,postassert,*win);
247:       MPI_Win_start(outgroup,startassert,*win);
248:     } break;
249:     default: SETERRQ(PetscObjectComm((PetscObject)sf),PETSC_ERR_PLIB,"Unknown synchronization type");
250:     }
251:   }
252:   return(0);
253: }

255: /*@C
256:    PetscSFFindWindow - Finds a window that is already in use

258:    Not Collective

260:    Input Arguments:
261: +  sf - star forest
262: .  unit - data type
263: -  array - array with which the window is associated

265:    Output Arguments:
266: .  win - window

268:    Level: developer

270: .seealso: PetscSFGetWindow(), PetscSFRestoreWindow()
271: @*/
272: static PetscErrorCode PetscSFFindWindow(PetscSF sf,MPI_Datatype unit,const void *array,MPI_Win *win)
273: {
274:   PetscSF_Window *w = (PetscSF_Window*)sf->data;
275:   PetscSFWinLink link;

278:   *win = MPI_WIN_NULL;
279:   for (link=w->wins; link; link=link->next) {
280:     if (array == link->addr) {
281:       *win = link->win;
282:       return(0);
283:     }
284:   }
285:   SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Requested window not in use");
286:   return(0);
287: }

289: /*@C
290:    PetscSFRestoreWindow - Restores a window obtained with PetscSFGetWindow()

292:    Collective

294:    Input Arguments:
295: +  sf - star forest
296: .  unit - data type
297: .  array - array associated with window
298: .  epoch - close an epoch, must match argument to PetscSFGetWindow()
299: -  win - window

301:    Level: developer

303: .seealso: PetscSFFindWindow()
304: @*/
305: static PetscErrorCode PetscSFRestoreWindow(PetscSF sf,MPI_Datatype unit,const void *array,PetscBool epoch,PetscMPIInt fenceassert,MPI_Win *win)
306: {
307:   PetscSF_Window *w = (PetscSF_Window*)sf->data;
309:   PetscSFWinLink *p,link;

312:   for (p=&w->wins; *p; p=&(*p)->next) {
313:     link = *p;
314:     if (*win == link->win) {
315:       if (array != link->addr) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Matched window, but not array");
316:       if (epoch != link->epoch) {
317:         if (epoch) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"No epoch to end");
318:         else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Restoring window without ending epoch");
319:       }
320:       *p = link->next;
321:       goto found;
322:     }
323:   }
324:   SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Requested window not in use");

326: found:
327:   if (epoch) {
328:     switch (w->sync) {
329:     case PETSCSF_WINDOW_SYNC_FENCE:
330:       MPI_Win_fence(fenceassert,*win);
331:       break;
332:     case PETSCSF_WINDOW_SYNC_LOCK:
333:       break;                    /* handled outside */
334:     case PETSCSF_WINDOW_SYNC_ACTIVE: {
335:       MPI_Win_complete(*win);
336:       MPI_Win_wait(*win);
337:     } break;
338:     default: SETERRQ(PetscObjectComm((PetscObject)sf),PETSC_ERR_PLIB,"Unknown synchronization type");
339:     }
340:   }

342:   MPI_Win_free(&link->win);
343:   PetscFree(link);
344:   *win = MPI_WIN_NULL;
345:   return(0);
346: }

348: static PetscErrorCode PetscSFSetUp_Window(PetscSF sf)
349: {
350:   PetscSF_Window *w = (PetscSF_Window*)sf->data;
352:   MPI_Group      ingroup,outgroup;

355:   PetscSFSetUpRanks(sf,MPI_GROUP_EMPTY);
356:   switch (w->sync) {
357:   case PETSCSF_WINDOW_SYNC_ACTIVE:
358:     PetscSFGetGroups(sf,&ingroup,&outgroup);
359:   default:
360:     break;
361:   }
362:   return(0);
363: }

365: static PetscErrorCode PetscSFSetFromOptions_Window(PetscOptionItems *PetscOptionsObject,PetscSF sf)
366: {
367:   PetscSF_Window *w = (PetscSF_Window*)sf->data;

371:   PetscOptionsHead(PetscOptionsObject,"PetscSF Window options");
372:   PetscOptionsEnum("-sf_window_sync","synchronization type to use for PetscSF Window communication","PetscSFWindowSetSyncType",PetscSFWindowSyncTypes,(PetscEnum)w->sync,(PetscEnum*)&w->sync,NULL);
373:   PetscOptionsTail();
374:   return(0);
375: }

377: static PetscErrorCode PetscSFReset_Window(PetscSF sf)
378: {
379:   PetscSF_Window  *w = (PetscSF_Window*)sf->data;
380:   PetscErrorCode  ierr;
381:   PetscSFDataLink link,next;
382:   PetscSFWinLink  wlink,wnext;
383:   PetscInt        i;

386:   for (link=w->link; link; link=next) {
387:     next = link->next;
388:     MPI_Type_free(&link->unit);
389:     for (i=0; i<sf->nranks; i++) {
390:       MPI_Type_free(&link->mine[i]);
391:       MPI_Type_free(&link->remote[i]);
392:     }
393:     PetscFree2(link->mine,link->remote);
394:     PetscFree(link);
395:   }
396:   w->link = NULL;
397:   for (wlink=w->wins; wlink; wlink=wnext) {
398:     wnext = wlink->next;
399:     if (wlink->inuse) SETERRQ1(PetscObjectComm((PetscObject)sf),PETSC_ERR_ARG_WRONGSTATE,"Window still in use with address %p",(void*)wlink->addr);
400:     MPI_Win_free(&wlink->win);
401:     PetscFree(wlink);
402:   }
403:   w->wins = NULL;
404:   return(0);
405: }

407: static PetscErrorCode PetscSFDestroy_Window(PetscSF sf)
408: {

412:   PetscSFReset_Window(sf);
413:   PetscFree(sf->data);
414:   PetscObjectComposeFunction((PetscObject)sf,"PetscSFWindowSetSyncType_C",NULL);
415:   PetscObjectComposeFunction((PetscObject)sf,"PetscSFWindowGetSyncType_C",NULL);
416:   return(0);
417: }

419: static PetscErrorCode PetscSFView_Window(PetscSF sf,PetscViewer viewer)
420: {
421:   PetscSF_Window *w = (PetscSF_Window*)sf->data;
423:   PetscBool      iascii;

426:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
427:   if (iascii) {
428:     PetscViewerASCIIPrintf(viewer,"  synchronization=%s sort=%s\n",PetscSFWindowSyncTypes[w->sync],sf->rankorder ? "rank-order" : "unordered");
429:   }
430:   return(0);
431: }

433: static PetscErrorCode PetscSFDuplicate_Window(PetscSF sf,PetscSFDuplicateOption opt,PetscSF newsf)
434: {
435:   PetscSF_Window        *w = (PetscSF_Window*)sf->data;
436:   PetscErrorCode        ierr;
437:   PetscSFWindowSyncType synctype;

440:   synctype = w->sync;
441:   if (!sf->setupcalled) {
442:     /* HACK: Must use FENCE or LOCK when called from PetscSFGetGroups() because ACTIVE here would cause recursion. */
443:     synctype = PETSCSF_WINDOW_SYNC_LOCK;
444:   }
445:   PetscSFWindowSetSyncType(newsf,synctype);
446:   return(0);
447: }

449: static PetscErrorCode PetscSFBcastBegin_Window(PetscSF sf,MPI_Datatype unit,const void *rootdata,void *leafdata)
450: {
451:   PetscSF_Window     *w = (PetscSF_Window*)sf->data;
452:   PetscErrorCode     ierr;
453:   PetscInt           i,nranks;
454:   const PetscMPIInt  *ranks;
455:   const MPI_Datatype *mine,*remote;
456:   MPI_Win            win;

459:   PetscSFGetRanks(sf,&nranks,&ranks,NULL,NULL,NULL);
460:   PetscSFWindowGetDataTypes(sf,unit,&mine,&remote);
461:   PetscSFGetWindow(sf,unit,(void*)rootdata,PETSC_TRUE,MPI_MODE_NOPUT|MPI_MODE_NOPRECEDE,MPI_MODE_NOPUT,0,&win);
462:   for (i=0; i<nranks; i++) {
463:     if (w->sync == PETSCSF_WINDOW_SYNC_LOCK) {MPI_Win_lock(MPI_LOCK_SHARED,ranks[i],MPI_MODE_NOCHECK,win);}
464:     MPI_Get(leafdata,1,mine[i],ranks[i],0,1,remote[i],win);
465:     if (w->sync == PETSCSF_WINDOW_SYNC_LOCK) {MPI_Win_unlock(ranks[i],win);}
466:   }
467:   return(0);
468: }

470: PetscErrorCode PetscSFBcastEnd_Window(PetscSF sf,MPI_Datatype unit,const void *rootdata,void *leafdata)
471: {
473:   MPI_Win        win;

476:   PetscSFFindWindow(sf,unit,rootdata,&win);
477:   PetscSFRestoreWindow(sf,unit,rootdata,PETSC_TRUE,MPI_MODE_NOSTORE|MPI_MODE_NOSUCCEED,&win);
478:   return(0);
479: }

481: PetscErrorCode PetscSFReduceBegin_Window(PetscSF sf,MPI_Datatype unit,const void *leafdata,void *rootdata,MPI_Op op)
482: {
483:   PetscSF_Window     *w = (PetscSF_Window*)sf->data;
484:   PetscErrorCode     ierr;
485:   PetscInt           i,nranks;
486:   const PetscMPIInt  *ranks;
487:   const MPI_Datatype *mine,*remote;
488:   MPI_Win            win;

491:   PetscSFGetRanks(sf,&nranks,&ranks,NULL,NULL,NULL);
492:   PetscSFWindowGetDataTypes(sf,unit,&mine,&remote);
493:   PetscSFWindowOpTranslate(&op);
494:   PetscSFGetWindow(sf,unit,rootdata,PETSC_TRUE,MPI_MODE_NOPRECEDE,0,0,&win);
495:   for (i=0; i<nranks; i++) {
496:     if (w->sync == PETSCSF_WINDOW_SYNC_LOCK) {MPI_Win_lock(MPI_LOCK_SHARED,ranks[i],MPI_MODE_NOCHECK,win);}
497:     MPI_Accumulate((void*)leafdata,1,mine[i],ranks[i],0,1,remote[i],op,win);
498:     if (w->sync == PETSCSF_WINDOW_SYNC_LOCK) {MPI_Win_unlock(ranks[i],win);}
499:   }
500:   return(0);
501: }

503: static PetscErrorCode PetscSFReduceEnd_Window(PetscSF sf,MPI_Datatype unit,const void *leafdata,void *rootdata,MPI_Op op)
504: {
505:   PetscSF_Window *w = (PetscSF_Window*)sf->data;
507:   MPI_Win        win;

510:   if (!w->wins) return(0);
511:   PetscSFFindWindow(sf,unit,rootdata,&win);
512:   MPI_Win_fence(MPI_MODE_NOSUCCEED,win);
513:   PetscSFRestoreWindow(sf,unit,rootdata,PETSC_TRUE,MPI_MODE_NOSUCCEED,&win);
514:   return(0);
515: }
516: static PetscErrorCode PetscSFFetchAndOpBegin_Window(PetscSF sf,MPI_Datatype unit,void *rootdata,const void *leafdata,void *leafupdate,MPI_Op op)
517: {
518:   PetscErrorCode     ierr;
519:   PetscInt           i,nranks;
520:   const PetscMPIInt  *ranks;
521:   const MPI_Datatype *mine,*remote;
522:   MPI_Win            win;

525:   PetscSFGetRanks(sf,&nranks,&ranks,NULL,NULL,NULL);
526:   PetscSFWindowGetDataTypes(sf,unit,&mine,&remote);
527:   PetscSFWindowOpTranslate(&op);
528:   PetscSFGetWindow(sf,unit,rootdata,PETSC_FALSE,0,0,0,&win);
529:   for (i=0; i<sf->nranks; i++) {
530:     MPI_Win_lock(MPI_LOCK_EXCLUSIVE,sf->ranks[i],0,win);
531:     MPI_Get(leafupdate,1,mine[i],ranks[i],0,1,remote[i],win);
532:     MPI_Accumulate((void*)leafdata,1,mine[i],ranks[i],0,1,remote[i],op,win);
533:     MPI_Win_unlock(ranks[i],win);
534:   }
535:   return(0);
536: }

538: static PetscErrorCode PetscSFFetchAndOpEnd_Window(PetscSF sf,MPI_Datatype unit,void *rootdata,const void *leafdata,void *leafupdate,MPI_Op op)
539: {
541:   MPI_Win        win;

544:   PetscSFFindWindow(sf,unit,rootdata,&win);
545:   /* Nothing to do currently because MPI_LOCK_EXCLUSIVE is used in PetscSFFetchAndOpBegin(), rendering this implementation synchronous. */
546:   PetscSFRestoreWindow(sf,unit,rootdata,PETSC_FALSE,0,&win);
547:   return(0);
548: }

550: PETSC_EXTERN PetscErrorCode PetscSFCreate_Window(PetscSF sf)
551: {
552:   PetscSF_Window *w = (PetscSF_Window*)sf->data;

556:   sf->ops->SetUp           = PetscSFSetUp_Window;
557:   sf->ops->SetFromOptions  = PetscSFSetFromOptions_Window;
558:   sf->ops->Reset           = PetscSFReset_Window;
559:   sf->ops->Destroy         = PetscSFDestroy_Window;
560:   sf->ops->View            = PetscSFView_Window;
561:   sf->ops->Duplicate       = PetscSFDuplicate_Window;
562:   sf->ops->BcastBegin      = PetscSFBcastBegin_Window;
563:   sf->ops->BcastEnd        = PetscSFBcastEnd_Window;
564:   sf->ops->ReduceBegin     = PetscSFReduceBegin_Window;
565:   sf->ops->ReduceEnd       = PetscSFReduceEnd_Window;
566:   sf->ops->FetchAndOpBegin = PetscSFFetchAndOpBegin_Window;
567:   sf->ops->FetchAndOpEnd   = PetscSFFetchAndOpEnd_Window;

569:   PetscNewLog(sf,&w);
570:   sf->data = (void*)w;
571:   w->sync  = PETSCSF_WINDOW_SYNC_FENCE;

573:   PetscObjectComposeFunction((PetscObject)sf,"PetscSFWindowSetSyncType_C",PetscSFWindowSetSyncType_Window);
574:   PetscObjectComposeFunction((PetscObject)sf,"PetscSFWindowGetSyncType_C",PetscSFWindowGetSyncType_Window);

576: #if defined(OMPI_MAJOR_VERSION) && (OMPI_MAJOR_VERSION < 1 || (OMPI_MAJOR_VERSION == 1 && OMPI_MINOR_VERSION <= 6))
577:   {
578:     PetscBool ackbug = PETSC_FALSE;
579:     PetscOptionsGetBool(NULL,NULL,"-acknowledge_ompi_onesided_bug",&ackbug,NULL);
580:     if (ackbug) {
581:       PetscInfo(sf,"Acknowledged Open MPI bug, proceeding anyway. Expect memory corruption.\n");
582:     } else SETERRQ(PetscObjectComm((PetscObject)sf),PETSC_ERR_LIB,"Open MPI is known to be buggy (https://svn.open-mpi.org/trac/ompi/ticket/1905 and 2656), use -acknowledge_ompi_onesided_bug to proceed");
583:   }
584: #endif
585:   return(0);
586: }